Many chairs that are used in commercial environments, such as office chairs, have a height adjustment mechanism for permitting the height of the chair to be raised or lowered to accommodate a user. Typically, the height adjustment mechanism includes a cylinder, such as a pneumatic cylinder (also known in the industry as a gas damper). By opening a valve in the cylinder, the height of the seat, with respect to the floor engaging portion of the chair, may be adjusted.
Many such chairs also have a seat tilt and/or a back tilt mechanism. Accordingly, the inclination of the seat and/or the inclination of the back rest may be adjusted. In some cases, synchronous tilt mechanisms are used, whereby the adjustment of the angle of the backrest occurs concurrently with the adjustment of the inclination of the seat. These adjustment mechanisms may also utilize a telescoping cylinder.
Mechanisms to adjust the height of a seat, the angle of inclination of a seat and the angle of the inclination of a backrest using a Bowden cable that is actuated by a push button are known. See for example U.S. Pat. Nos. 5,577,804 and 6,019,429 by the applicant.
From time to time, a cylinder may be damaged during use, or a seal may fail. In such cases, the cylinder must be replaced if the chair is to maintain its functionality.